UNIVERSALLY DISTRIBUTED SPECIES. 75 



point. The marginals are low and wide, the reflection as broad as the 

 base of attachment, reaching nearly to its lower edge, and furnished 

 with one inner, long, bhmtl.y bifid, stont, oblique cutting point, and 

 two or more short outer cutting points. The same form of marginal is 

 found in Pnpa. The membrane is very peculiar in the lateral teeth, 

 not only from their large size, but also from their symmetrical, tricuspid 

 reflection, quite like the nsual arrangement of central teeth in the Sel- 

 icidcc. Similar lateral teeth are found in Zonites GundlacM. 



Ilelicodiscus lincntus. Say. 



Shell widely umbilicated, discoidal; epidermis greenish; whorls 

 about 4, visible on the base of the shell as well as ^ ^, 



' J IG. ol , 



above, with numerous equidistant, parallel, raised lines ^r=-._,.__:_, 

 revolving upon them; suture much impressed ; apertun 

 remote from the axis, semi lunate, narrow, not expanding; 

 peristome acute, thin; umbilicus wide, forming a con 

 cave depression of the base, each volution visible to the 

 apex ; within the aperture, on the external circumference, 



1 1 ,■ -f i r, • r. • . 1 1 -J J .1 llei. lineatus, 



are placed irom 1 to o,i)airs ot minute, conical, white teeth, eniai-ed. 

 the first pair in sight when looking into the aperture, the others more 

 remote. Greater diameter 3.^""", lesser S"^"^ ; height, 1^"™. 



Melix Uneata, Say, Jouni. Phila. Acad., i, 18 (1817) ; ii, 273 (1824) ; Nicb. Encycl., Sd 

 ed., iv (1819); Binney's ed. 7, 24.— Binney, Bost.Jouru. Nat. Hist., iii, 

 436, pi. xxii, fig. 6 (1840;; Terr. Moll., ii, 261, pi. xlviii, fig. 1.— De Kay, 

 N. Y. Moll., 44(1843).— Gould, Invert., 179, fig. 103 (1841).— Adams, Vermout 

 Mollusca, 161 (1842).— Fekussac, Tab. Syst., 44; Hist., pi. Ixxix, tig. 1.— 

 Deshayes luFer.,i, 80.— Chemnitz, 2d ed., ii, 203, tab. ci, figs. 1.3-15. — 

 Pfeiffer, Mod. Hel. Viv., i, 184.- Reeve, Coii. Icou., 724 (1852).— W. G. 

 Bisney, Terr. Moll., iv, 123.— Morse, Amer. Nat., i, 546, fig. 44 (1867). 



Planorhis lun-aUdus, Say (?), Proc. Acad. Nat. Sci., ii, 164 (1821) ; ed.BiNNEY, 63. 



Eualina f Uneata, W. G. Binney, L. & Fr.-W. Sh., i, 52 (1869).— GouLD aud BiNNEY, 

 Invert, of Mass., ed. 2, p. 404 (1870). 



Helicodiscus Uneata, Morse, Jouru. Port!. Soc, i, 25, figs. 61, C2 ; pi. ii, fig. 3 ; pi. vii, 

 fig. 63 (1864).— Tyron, Am. Journ. Conch., ii, 264 (1866).— W. G. BiNNEvi 

 T. M., V, 185. 



Inhabits all of the Eastern, Central, aud Pa- 

 ific Provinces, having been found from Gaspe 

 to Texas j on the Eio Chama, New Mexico ; in 

 Idaho; in Oakland,Cal. Ja-w oiuneatus. 



Jaw : see Fig. 37 A. 



Lingual membrane : see p. 74. 



Animal (see p'. 74) nearly white or rather translucent, mottled with 

 small white blotches ; body long and narrow ; upper posterior portion. 



